TITLE OF THE INVENTION
APPARATUS FOR REDUCING CARBON DIOXIDE BY USING MOLTEN
SLAG
CROSS-REFERENCE TO RELATED APPLICATION
This application claims priority to and the benefit of Korean Patent
Application No. 10-201 1-0140222 filed in the Korean Intellectual Property Office
on December 22, 201 1, the entire contents of which are incorporated herein by
reference.
10
BACKGROUND OF THE INVENTION
(a) Field of the Invention
The present invention relates to an apparatus for reducing carbon
dioxide, and more particularly, to an apparatus for reducing carbon dioxide
15 using molten slag at high temperatures and an offgas including carbon dioxide
exhausted in a process of manufacturing ingot iron.
(b) Description of the Related Art
Of the total amount of carbon dioxide generated in Korea, the amount
exhausted in the steel industry is 20 % or more, of which the amount exhausted
20 in a process of manufacturing ingot iron using a blast furnace, a multi-stage
fluidized bed type of reducing furnace, and a melt-down gasifier, is 90 % or
more.
If an offgas generated in the process of manufacturing the ingot iron
using a blast furnace operation, the multi-stage fluidized bed type reducing
furnace, and the melt-down gasification is exhausted to the air as it is, the
exhaust is harmful to the environment and misuses reusable components,
which is not preferable in views of resource and energy efficiencies.
Further, carbon dioxide included in the offgas generated in the process
5 of manufacturing the ingot iron is considered as a factor of climate change, and
needs to be collected to reduce generation of carbon dioxide.
In order to remove carbon dioxide from the offgas generated in the
process of manufacturing the ingot iron, additional equipment is required, which
may become an obstacle in economically manufacturing the ingot iron.
10 In the case of the related art, alkali oxides and carbon dioxide from
molten slag are reacted to fixate (isolate) carbon dioxide. A fixation reaction
aims at collection of carbon dioxide and collection of reaction heat generated in
the reaction to increase fixed energy efficiency, but has a problem in that
reactivity of alkali oxides of the slag with carbon dioxide is not good as
15 compared to alkali oxides included in quicklime and dolomite, and thus the
fixation reaction is not effective in views of fixation of carbon dioxide and the
collection of reaction heat.
Accordingly, there is a situation in which a technology of reducing
carbon dioxide using high heat of the slag in addition to the fixation of carbon
20 dioxide through the slag is required.
A temperature of the slag exhausted during the process of
manufacturing the ingot iron is about 1500 "C. Generally, the molten slag at
high temperatures is cooled to room temperature to be solidified, thus being
used as a raw material of cement. Assuming that 300 kg of the slag per ton of
a hot melt is generated, heat wasted according to cooling to room temperature
is 444 MJ when generating the slag per ton of the hot melt.
Since an enormous amount of slag is exhausted in the process of
manufacturing the ingot iron, if sensible heat of the slag wasted in Korea and
5 abroad is used to reuse and reduce carbon dioxide, the sensible heat may help
to secure competitiveness for the process of manufacturing the ingot iron.
The above information disclosed in this Background section is only for
enhancement of understanding of the background of the invention and therefore
it may contain information that does not form the prior art that is already known
lo in this country to a person of ordinary skill in the art.
SUMMARY OF THE INVENTION
The present invention has been made in an effort to provide an
apparatus for reducing carbon dioxide and a method of reducing carbon dioxide,
in which carbon dioxide exhausted during a process of manufacturing ingot iron
15 is capable of being reacted with powdered coal to reduce carbon dioxide using
heat (sensible heat and latent heat) of molten slag at high temperatures
generated in the process of manufacturing the ingot iron.
An exemplary embodiment of the present invention provides an
apparatus for reducing carbon dioxide including: a slag atomizer spraying a
20 molten slag to form slag particulates; a reaction chamber connected to the slag
atomizer, allowing a mixture gas including carbon dioxide and a powdered coal
to be blown thereinto, and reacting the carbon dioxide with the powdered coal
by heat generated when the slag particulates are formed; and a carbonization
reaction furnace connected to the reaction chamber by a particulate transfer
conduit, allowing an offgas exhausted in a process of manufacturing an ingot
iron and the powdered coal to be blown thereinto, and reacting the slag
particulates supplied from the reaction chamber through the particulate transfer
conduit with carbon dioxide included in the offgas exhausted in the process of
5 manufacturing the ingot iron, in which the mixture gas blown into the reaction
chamber is supplied from the carbonization reaction furnace through a mixture
gas supply conduit.
The apparatus for reducing carbon dioxide may further include an offgas
supply conduit supplying the offgas exhausted in the process of manufacturing
lo the ingot iron to the carbonization reaction furnace, and a powdered coal supply
device branched from the offgas supply conduit to supply the powdered coal to
the offgas supply conduit.
The apparatus for reducing carbon dioxide may further include a heating
device connected to the offgas supply conduit and combusting tar or a
15 hydrocarbon compound from the offgas exhausted in the process of
manufacturing the ingot iron.
The carbonization reaction furnace may be a fluidized bed type of
carbonization reaction furnace.
Another exemplary embodiment of the present invention provides a
20 method of reducing carbon dioxide, including: providing a molten slag; charging
the molten slag into a slag atomizer to form slag particulates; blowing a mixture
gas including a powdered coal and carbon dioxide into a reaction chamber and
reacting the powdered coal with the carbon dioxide by using heat generated
when the slag particulates are formed; and charging the slag particulates
exhausted in the reaction chamber into a carbonization reaction furnace, and
then blowing an offgas exhausted in a process of manufacturing an ingot iron
and the powdered coal to react the slag particulates with the offgas exhausted
in the process of manufacturing the ingot iron, in which the mixture gas blown
5 into the reaction chamber is supplied from the carbonization reaction furnace.
The method of reducing carbon dioxide may further include heating the
offgas exhausted in the process of manufacturing the ingot iron to remove tar or
a hydrocarbon compound included in the offgas.
According to the exemplary embodiments of the present invention, in an
lo apparatus for reducing carbon dioxide, it is possible to generate carbon
monoxide by reacting an offgas including carbon dioxide with a powdered coal
by using heat of molten slag at high temperatures, which is a byproduct
generated in a process of manufacturing ingot iron. Thus, generated carbon
monoxide can be transported to the process of manufacturing the ingot iron in
15 order to be reused in the reduction of an iron ore.
Further, it is possible to additionally sequester carbon dioxide by
reacting the slag cooled by reaction heat of the aforementioned reaction with
carbon dioxide.
BRIEF DESCRIPTION OF THE DRAWINGS
20 FIG. 1 is a view schematically illustrating a constitution of an apparatus
for reducing carbon dioxide according to the present invention.
FIG. 2 is a process view of a method of reducing carbon dioxide
according to the present invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS
Advantages and features of the present invention and methods to
achieve them will be elucidated from exemplary embodiments described below
in detail with reference to the accompanying drawings. Further, exemplary
embodiments introduced herein are provided to make disclosed contents
5 thorough and complete and sufficiently transfer the spirit of the present
invention to those skilled in the art. Therefore, the present invention will be
defined only by the scope of the appended claims. Like reference numerals
designate like elements throughout the specification.
Hereinafter, an apparatus for reducing carbon dioxide according to a
lo preferable exemplary embodiment of the present invention will be described
with reference to the accompanying drawings. For reference, in the
description of the present invention, in the case where it is deemed that a
detailed description of related known functions or constitutions may
unnecessarily cloud the gist of the present invention, the detailed description
15 thereof will be omitted.
FIG. 1 is a view schematically illustrating a constitution of the apparatus
for reducing carbon dioxide according to the present invention.
As illustrated in FIG. 1, the apparatus for reducing carbon dioxide
according to the present invention includes
20 a slag atomizer 10 spraying a molten slag to form slag particulates, a
reaction chamber 20 connected to the slag atomizer 10, allowing a mixture gas
including carbon dioxide and a powdered coal to be blown thereinto, and
reacting the carbon dioxide with the powdered coal by heat generated when the
slag particulates are formed, and a carbonization reaction furnace 40 connected
to the reaction chamber 20 by a particulate transfer conduit 30, allowing an
offgas exhausted in a process of manufacturing ingot iron and the powdered
coal to be blown thereinto, and reacting the slag particulates supplied from the
reaction chamber 20 through the particulate transfer conduit 30 with carbon
5 dioxide included in the offgas exhausted in the process of manufacturing the
ingot iron, in which the mixture gas blown into the reaction chamber 20 is
supplied from the carbonization reaction furnace 40 through a mixture gas
supply conduit 50.
The molten slag is exhausted as a byproduct of the process of
lo manufacturing the ingot iron, and includes calcium oxide (CaO), magnesium
oxide (MgO), and the like, and a temperature thereof may be about 1500 "C or
. more.
Since the molten slag has a very high temperature, sensible heat and
latent heat possessed in the molten slag are emitted in a process of cooling to
15 room temperature. For example, assuming that 300 kg of the slag per ton of a
hot melt is generated, heat generated per ton of the hot melt by cooling of the
slag is about 444 MJ.
The process of manufacturing the ingot iron includes a blast furnace
operation process of charging a sintered ore and a coke to manufacture the
20 ingot iron, and also includes a COREX@ process of manufacturing the ingot iron
by using a multi-stage fluidized bed type of reducing furnace, a packed layer
type of reducing furnace of a FINEX@ process of manufacturing the ingot iron by
using a melt-down gasifier, and a melt-down gasifier.
If the molten slag is charged into the slag atomizer 10, the molten slag
falls by gravity force and is sprayed into the reaction chamber 20 connected to
the slag atomizer 10 through a fine slit to form the fine slag particulates.
The slag atomizer 10 has a funnel shape having an exterior diameter
that is decreased toward a lower end thereof, and the molten slag is charged
5 thereinto and sprayed through the slit having a size of 1 mm or less, which is
formed at the lower end, by gravity force to form the slag particulates. A
temperature of the slag particulates formed by spraying the molten slag at high
temperatures is in a range of about 1000 "C.
Meanwhile, spraying of the slag may be accelerated by introducing a
lo gas spraying device (not illustrated) to the slag atomizer 10 so that the molten
slag particulates are easily formed.
Specific gravity of the slag is about 2.6, and surface tension of the slag
is about 0.40 ~lm'.
When the molten slag is sprayed through the fine slit of the atomizer,
15 fine droplets of 1 mm or less are formed. Specific surface area of the fine
droplet is 2.3 m2/kg, which is very wide, and thus an area through which heat is
capable of being emitted is very wide.
In more detail, when the molten slag is sprayed through the slit, since
surface tension of the slag is about 0.4 ~lm',w hich is very high, it is possible to
20 form a slag powder having a particle size in the wide range of 10 pm to 1 mm by
Plateau-Rayleigh instability which is one of widely known instability phenomena
of a fluid.
The temperature of the molten slag is about 1500 "C, but is very rapidly
cooled to 1000 "C when the molten slag is sprayed to form the slag particulates,
and in this case, a generated heating value is 151 MJ per ton of the hot melt by
the following equation.
1.004 kJ/kg°C x (1 500 "C-1000 "C) x 300 kglton of hot metal
= 151 MJIton of hot metal .... (3)
The heating value generated as described above helps a Boudouard
reaction of the powdered coal and the carbon dioxide from the mixture gas
containing the powdered coal and the carbon dioxide, which are supplied from
the carbonization reaction furnace 40, in the reaction chamber 20.
A reaction equation of the Boudouard reaction is as follows.
10 CO2 + C = 2C0 (reaction heat: 160 kJ1mol) . . .. (4)
A quantity of heat generated by Equation 3 reduces 938 mol of carbon
dioxidelton of a hot metal (41 kg of C02/ton of the hot metal) and generates
1,876 mol of carbon monoxidelton of the hot metal by the Boudouard reaction
where carbon dioxide and carbon are reacted to generate carbon monoxide.
15 The generated carbon monoxide is exhausted through an offgas conduit 25 of
the reaction chamber, and may be reused for reduction of the iron ore in the
process of manufacturing the ingot iron.
If an amount of carbon monoxide is converted into the amount of carbon,
the amount of carbon becomes 22 kglton of the hot metal, and assuming that
20 the use amount of carbon during the process of manufacturing the ingot iron, for
example, a blast furnace process is about 400 kglton of the hot metal, if carbon
dioxide is reused by using the molten slag, the use amount of carbon saved
during the process of manufacturing the ingot iron may be about 5 %.
The slag particulates falling in the reaction chamber 20 are cooled to be
charged through the particulate transfer conduit 30 into the carbonization
reaction furnace 40 by gravity force. The carbonization reaction furnace 40
allows the offgas containing carbon dioxide exhausted in the process of
manufacturing the ingot iron and the powdered coal to be blown thereinto.
5 The powdered coal and the offgas containing carbon dioxide form a
fluidized bed in the carbonization reaction furnace 40, and the slag particulates
and the carbon dioxide are reacted to carbonize an alkali salt in the slag, thus
removing the carbon dioxide.
The carbonization reaction of the alkali salt and the carbon dioxide in the
lo slag particulates may be represented by the following equation.
CaO + COz -t CaC03 (reaction heat: 179 kJ1mol) .... (1)
MgO + COz -t MgC03 (reaction heat: 117 kJ1mol) .... (2)
The carbonization reaction furnace 40 may be maintained at 700 to 800
"C by the reaction heat and combustion heat of tar or a hydrocarbon compound
15 in the offgas containing carbon dioxide in a heating device 80 as will be
described below.
Since the carbonization reaction of the alkali salt is a reaction removing
a gas, a gas volume is reduced by the reaction. Therefore, in order to increase
reaction efficiency, a high pressure operation is required, and in the case where
20 a pressure of the carbonization reaction furnace 40 is maintained at 5 to 10 bar,
the case may be useful to increase a reaction speed.
The slag particulates reacted with carbon dioxide in the carbonization
reaction furnace 40 are precipitated as carbonates to be exhausted through a
carbonate exhaustion pipe 45 to the outside.
The powdered coal blown into the carbonization reaction furnace 40
while being mixed with the offgas containing carbon dioxide is preliminarily
heated by internal heat of the carbonization reaction furnace 40.
Since the reaction speed of the alkali salt in the slag particulates and
5 carbon dioxide is not high because of the reaction in a solid state, carbon
dioxide, which is not involved in the reaction, is exhausted together with the
preliminarily heated powdered coal from the carbonization reaction furnace 40
to be blown into the reaction chamber 20 through a mixture gas conduit.
That is, a supply source of the mixture gas including carbon dioxide and
lo the powdered coal blown into the reaction chamber 20 becomes the offgas
containing unreacted carbon dioxide, which is not involved in the carbonization
reaction but is exhausted from the carbonization reaction furnace 40, and the
powdered coal.
Meanwhile, the offgas exhausted in the process of manufacturing the
15 ingot iron is blown into the heating device 80 before being blown into the
carbonization reaction furnace 40, and thus air or oxygen is blown to combust
the tar or the hydrocarbon compound existing in the offgas. Carbon dioxide in
the offgas is concentrated by combusting the tar and the hydrocarbon
compound.
20 A combustion reaction of the tar and the like occurring in the heating
device 80 is represented by the following Equation 3.
C + O2 + CO2 (reaction heat: 396 kJ1mol) ---- (3)
The temperature of the offgas containing carbon dioxide may be
additionally increased by the reaction heat.
As the offgas exhausted in the process of manufacturing the ingot iron, it
is possible to use a carbon dioxide tail-gas (C02 tail-gas) that is the offgas
including carbon dioxide at a high concentration by separating only carbon
dioxide of the offgas.
5 The offgas exhausted in the process of manufacturing the ingot iron, in
which carbon dioxide is concentrated, is blown into the carbonization reaction
furnace 40 through an offgas supply conduit 60, and the powdered coal is blown
into the carbonization reaction furnace 40 from a powdered coal supply device
70 through a pipe branched from the offgas supply conduit 60 while being
lo mixed with the offgas in the offgas supply conduit 60.
The powdered coal and the offgas containing carbon dioxide blown into
the carbonization reaction furnace 40 are reacted with the slag particulates in
the fluidized bed in the carbonization reaction furnace 40, while being heated, to
cause carbonization of the slag particulates.
15 FIG. 2 is a process view of a method of reducing carbon dioxide
according to the present invention.
The method of reducing carbon dioxide according to the present
invention includes providing a molten slag (SIO), charging the molten slag into a
slag atomizer 10 to form slag particulates (S20), blowing a mixture gas including
20 powdered coal and carbon dioxide into a reaction chamber 20, and reacting the
powdered coal with the carbon dioxide by using heat generated when the slag
particulates are formed (S30), and charging the slag particulates exhausted in
the reaction chamber 20 into a carbonization reaction furnace 40, and then
blowing an offgas exhausted in a process of manufacturing an ingot iron and
the powdered coal to react the slag particulates with the offgas exhausted in the
process of manufacturing the ingot iron (S40), in which the mixture gas blown
into the reaction chamber 20 is supplied from the carbonization reaction furnace
40.
5 Additionally, the method of reducing carbon dioxide further includes
heating the offgas exhausted in the process of manufacturing the ingot iron to
remove tar or a hydrocarbon compound included in the offgas.
In the present invention, a large amount of carbon dioxide may be
reduced by reacting the offgas where carbon dioxide exhausted in the process
lo of manufacturing the ingot iron is concentrated in the carbonization reaction
furnace to remove a portion of carbon dioxide, and blowing the offgas
containing residual carbon dioxide, which is not involved in the reaction in the
carbonization reaction furnace, and the powdered coal into the gas chamber to
perform the reaction by using heat of the molten slag.
15 Although the exemplary embodiments of the present invention have
been described with reference to the accompanying drawings, it will be
apparent to those skilled in the art that various modifications and changes may
be made thereto without departing from the technical spirit or essential feature
of the invention.
20 Therefore, it is understood that the above exemplary embodiments are
illustrative only but are not limitative. The scope of the present invention is
represented by the claims as described later rather than the detailed description,
and it is to be construed that all modifications and modified embodiments
deduced from the meaning and the scope of the claims, and the equivalent
13
concept thereto are included within the scope of the present invention.
WHAT IS CLAIMED IS:
1. An apparatus for reducing carbon dioxide comprising:
a slag atomizer spraying a molten slag to form slag particulates;
5 a reaction chamber connected to the slag atomizer, allowing a mixture
gas including carbon dioxide and a powdered coal to be blown thereinto, and
reacting the carbon dioxide and the powdered coal by heat generated when the
slag particulates are formed; and
a carbonization reaction furnace connected to the reaction chamber by a
lo particulate transfer conduit, allowing an offgas exhausted in a process of
manufacturing ingot iron and the powdered coal to be blown thereinto, and
reacting the slag particulates supplied from the reaction chamber through the
particulate transfer conduit with carbon dioxide included in the offgas exhausted
in the process of manufacturing the ingot iron,
15 wherein the mixture gas blown into the reaction chamber is supplied
from the carbonization reaction furnace through a mixture gas supply conduit.
2. The apparatus for reducing carbon dioxide of claim 1, further
comprising:
20 an offgas supply conduit supplying the offgas exhausted in the process
of manufacturing the ingot iron to the carbonization reaction furnace; and
a powdered coal supply device branched from the offgas supply conduit
to supply the powdered coal to the offgas supply conduit.
3. The apparatus for reducing carbon dioxide of claim 2, further
comprising
a heating device connected to the offgas supply conduit and combusting
tar or a hydrocarbon compound from the offgas exhausted in the process of
5 manufacturing the ingot iron.
4. The apparatus for reducing carbon dioxide of claim 1, wherein
the carbonization reaction furnace is a fluidized bed type of
carbonization reaction furnace.
10
5. A method of reducing carbon dioxide, comprising:
providing molten slag;
charging the molten slag into a slag atomizer to form slag particulates;
blowing a mixture gas including powdered coal and carbon dioxide into
15 a reaction chamber, and reacting the powdered coal with the carbon dioxide by
using heat generated when the slag particulates are formed; and
charging the slag particulates exhausted in the reaction chamber into a
carbonization reaction furnace, and then blowing an offgas exhausted in a ~ process of manufacturing ingot iron and the powdered coal to react the slag
20 particulates with the offgas exhausted in the process of manufacturing the ingot ~ iron,
wherein the mixture gas blown into the reaction chamber is supplied
I from the carbonization reaction furnace.
6. The method of claim 5, further comprising
heating the offgas exhausted in the process of manufacturing the ingot
iron to remove tar or a hydrocarbon compound included in the offgas.